1. Field of the Invention
The present invention relates to a plasma display apparatus.
2. Description of the Related Art
A plasma display apparatus (PDP) comprises a plasma display panel having two glass substrates disposed in opposition, and a driving and controlling circuit part. One of the glass substrates has a plurality of parallel address electrodes, and the other glass substrate has a plurality of sustain electrodes disposed in parallel to each other and perpendicular to the address electrodes. The sustain electrodes include X electrodes and Y electrodes disposed alternately. Display cells are formed between two adjacent X electrode and Y electrode. The circuit part is disposed on the external surface of one of the glass substrates of the plasma display panel, and includes several rigid substrates. A flexible substrate is used for connecting electrodes of the plasma display panel and the rigid substrate.
The plasma display apparatus is disclosed in, for example, Japanese Unexamined Patent Publication (Kokai) No. 11-327503, and No. 11-327458.
Since the flexible substrate is flexible, it is necessary to use the flexible substrate at a curved portion. However, the flexible substrate is expensive, and the price thereof is two times the cost of a normal rigid substrate. Further, since the flexible substrate is used at the bent portion, warpage or breakage is apt to occur. Examples in which reinforcing patterns are provided at the peripheries of flexible substrates are disclosed in Japanese Unexamined Patent Publication (Kokai) No. 61-131492 and Japanese Unexamined Utility Model Publication (Kokai) No. 6-45364.
In the plasma display apparatus, the flexible substrate is used as a composite substrate or an electronic circuit module in which the flexible substrate is coupled and adhered to the rigid substrate. Therefore, the portion of the flexible substrate superimposed or the rigid substrate has no problem of warpage or breakage, which is likely to occur in an individual flexible substrate.
However, at the portion of superimposed portion between the rigid substrate and the flexible substrate, the rigid substrate holds bare chips, and the flexible substrate has apertures for exposing the bare chips and bonding pads, so that terminals of the bare chips and the bonding pads of the flexible substrate are connected together with bonding wires. In carrying out wire bonding, it is not possible to achieve wire bonding if there is a deviation between the position of the terminals of the bare chips and the position of the bonding pads of the flexible substrate. In many cases, the positional deviation occurs due to degradation in the precision of the size of the flexible substrate, particularly the degradation in the precision of the size around the aperture of the flexible substrate. The precision of the size around the aperture of the flexible substrate is degraded due to thermal contraction in the wire bonding at the time of connecting the flexible substrate to the rigid substrate.
Therefore, conventionally, the outer shape of the flexible substrate is designed to have a relatively large size, in particular, a relatively large size has been used for the width from the aperture of the flexible substrate to the outer edge thereof, thereby to try to prevent the degradation in the positional precision at the peripheral region of the aperture of the flexible substrate.
However, since the flexible substrate is expensive, the increase in the size of the outer shape of the flexible substrate leads to an increase in cost. Therefore, it has been desired to avoid occurrence of a positional deviation between the position of the terminals of the bare chip and the position of the bonding pads of the flexible substrate, without increasing the size of the outer shape of the flexible substrate.
Further, the flexible substrate is easily broken at a position that is brought into contact with the outer edge of the rigid substrate. Further, the flexible substrate is broken or distorted at a position on the outside of the rigid substrate. Further, as a high voltage is used in the plasma display apparatus, it has been desired to reduce the inductance of the conductor patterns of the flexible substrate.
It is an object of the present invention to provide a plasma display apparatus in which a satisfactory wire bonding can be carried out without increasing the size of the outer shape of a flexible substrate.
It is another object of the present invention to provide a plasma display apparatus capable of preventing occurrence of breakage or warpage of a flexible substrate.
It is still another object of the present invention to provide a plasma display apparatus capable of reducing the inductance of conductor patterns of a flexible substrate.
According to one aspect of the present invention, there is provided a plasma display apparatus comprising a plasma display panel having a plurality of electrodes for emission of light, an electronic circuit module including a rigid substrate having at least one chip, and a flexible substrate coupled to the rigid substrate and having a first portion with an aperture for exposing the chip and bonding pads and a second portion positioned on the outside of the rigid substrate, bonding wires connecting terminals of the chip with the bonding pads of the flexible substrate, and a reinforcing pattern provided in at least the first portion of the flexible substrate.
In this structure, the reinforcing pattern is provided in at least the first portion of the flexible substrate coupled to the rigid substrate. The reinforcing pattern is formed with a metal material that is the same as the metal material of conductor patterns. When the flexible substrate is connected to the rigid substrate or when the flexible substrate is wire bonded, a metal material does not thermally contract as easily as a resin that constitutes the flexible substrate. Therefore, a positional deviation does not occur easily. As a result, even when a distance from the aperture of the flexible substrate to the outer edge is decreased thereby relatively decreasing the size of the outer shape of the flexible substrate, the positional precision at portions around the aperture of the flexible substrate is not degraded. As the size of the outer shape of the flexible substrate can be made relatively small, it is possible to achieve a cost reduction.
According to another aspect of the present invention, there is provided a plasma display apparatus comprising a plasma display panel having a plurality of electrodes for emission of light, an electronic circuit module including a rigid substrate, and a flexible substrate coupled to the rigid substrate and having conductor patterns electrically connected to the electrodes of the plasma display panel, and a reinforcing pattern provided in a layer of the flexible substrate separate from a layer on which the conductor patterns exist.
In this structure, since the reinforcing pattern is provided in the layer of the flexible substrate separate from the layer on which conductor patterns exist, it is possible to prevent occurrence of breakage or warpage of the flexible substrate. Further, when a high voltage is applied to the conductor patterns of the flexible substrate, an eddy current is generated in the reinforcing pattern disposed opposite to the conductor patterns, based on an electromagnetic inductance. As a result, it is possible to reduce the inductance of the conductor patterns. Consequently, it is possible to obtain satisfactory display characteristics.
Preferably, the reinforcing pattern is provided at a position overlapping with the conductor patterns. For example, the reinforcing pattern is provided as a conductor film that extends along the outer edge of the rigid substrate. Although the flexible substrate is weak at a portion that is brought into contact with the outer edge of the rigid substrate, the flexible substrate is not easily broken as this flexible substrate is reinforced with the reinforcing pattern. Alternatively, the reinforcing pattern is provided as a completely covering conductor film on the portion of the flexible substrate positioned on the outside of the rigid substrate. Alternatively, the reinforcing pattern is provided as a conductor film including conductor strips provided corresponding to the individual conductor strips of the conductor patterns. As a result, the flexible substrate is not easily deformed, and the conductor patterns of the flexible substrate are not broken.
According to still another aspect of the present invention, there is provided a plasma display apparatus comprising a plasma display panel having a plurality of electrodes for emission of light, an electronic circuit module including a rigid substrate, and a flexible substrate coupled to the rigid substrate and having conductor patterns electrically connected to the electrodes of the plasma display panel, and a dummy pattern provided on the rigid substrate.
In this structure, when a high voltage is applied to conductor patterns of the flexible substrate, an eddy current is generated in the dummy pattern disposed opposite to the conductor patterns, based on an electromagnetic inductance. As a result, it is possible to reduce the inductance of the conductor patterns. Consequently, it is possible to obtain satisfactory display characteristics.
According to still another aspect of the present invention, there is provided a plasma display apparatus comprising a plasma display panel having a plurality of electrodes for emission of light, an electronic circuit module including a rigid substrate, and a flexible substrate coupled to the rigid substrate and having conductor patterns electrically connected to the electrodes of the plasma display panel, and an electric part having a first portion fixed to the flexible substrate and a second portion fixed to the rigid substrate.
In this structure, the electric part is disposed extending over the rigid substrate and the flexible substrate, thereby to electrically interconnect the rigid substrate and the flexible substrate. Therefore, it is possible to decrease the number of wires connecting the rigid substrate and the flexible substrate.